A tight-reflective photomask utilizing extreme ultraviolet (EUV) light having a wavelength of about 13.5 nm is proposed as a lithographic technique contrived to deal with miniaturization of semiconductor devices. A light-reflective photomask for EUV exposure normally includes a multilayer reflection layer formed on a glass substrate, and light-absorber formed on the multilayer reflection layer.
In the above-mentioned light-reflective photomask, a phenomenon called a shadowing effect becomes a problem. That is, in lithography using a light-reflective photomask, exposure light (EUV light) is made incident on the photomask from a direction deviated from the vertical direction. For this reason, a shadow is created by a convex part of a circuit pattern formed on the light-absorber. Such a phenomenon is the shadowing effect. This shadowing effect can be prevented from occurring by reducing the thickness of the light-absorber. However, when the thickness of the light-absorber is reduced, the light-absorbing characteristic of the light-absorber is lowered, and the reflectivity of the light-absorber is increased. As a result, a problem that reflected light from the light-absorber affects the adjacent area to thereby adversely affect lithography is caused.
Regarding a solution of such a problem, a way of securing the low reflectivity by removing the light-absorber and multilayer reflection layer of the area outside the circuit pattern area is conceivable.